LONDON -- British voters were choosing lawmakers Thursday in an election deemed too close to call - circumstances that are widely predicted to produce an ambiguous result and lead to frantic political horse-trading.
Polls put Prime Minister David Cameron's Conservatives and Ed Miliband's Labour Party in a dead heat, and neither looks able to win a majority of Parliament's 650 seats.
Many voters are turning elsewhere - chiefly to the separatist Scottish National Party, which will dominate north of the border, and the anti-immigrant U.K. Independence Party. UKIP is third in opinion polls but Britain's electoral system means it can win at most a handful of seats.
If no party wins outright, it may take days or weeks of negotiation to forge a workable government.
CBS News correspondent Charlie D'Agata reports from London that the special relationship with the U.S. was unlikely to change no matter who is in power.
However, both main parties have promised cuts in military spending, and U.S. top brass has already expressed concerns that America's strongest ally might not be capable in playing a central role in global affairs, D'Agata reports.
The carefully stage-managed campaign lacked impromptu drama. But television debate appearances in which the public put questions directly to the politicians made plain that many distrust promises to safeguard the economy, preserve the National Health Service from severe cutbacks and control the number of migrants from the European Union.
Cameron and Miliband were both up early to vote. The prime minister voted in his Oxfordshire constituency with his wife, Samantha, while Miliband cast his ballot alongside his wife, Justine, in northern England. Liberal Democrat leader Nick Clegg walked hand-in-hand with his wife Miriam to the polls in the city of Sheffield.
Voters headed for schools, halls, pubs, gyms and churches to make their voices heard all across this island nation of 64 million people. In the bright early-morning sunshine in London, voters cast ballots at a polling station close to Parliament as police stood guard.
Signs of the unfolding political drama were all around. The squares opposite Parliament were packed with temporary outdoor television studios, while commuters picked up newspapers urging voters to the polls.
"It's going to be important for Britain for the next five years," said Gerry McQuillan, 61, an arts administrator voting Labour. "We're coming out of economic austerity but we've got to get the right government for the next five years."
Alexis Thomas, 34, a doctor, was mindful of all the predictions of a dead heat and wanted to make her voice heard.
"Because it's so tight, I think that if I didn't come out and vote, and didn't get the result that I wanted, then I'd only have myself to blame," Thomas said - though she wasn't saying what result that was.
About 50 million people were registered to vote, and early indications are that turnout will be high. There was an excitement about taking part - if only for the pleasure of being involved in a big national event.
Many used social media to spread the news that they've voted. Facebook said that for the first time in a British general election, users have access to the "I'm a Voter" button. More than 1.3 million people had used it as of Thursday morning.
Dogs and other creatures also featured on polling day. The hashtag #DogsAtPollingStations was one of the top 10 trends in Britain on Twitter, where many people posted fun photos of pups they took to - or spotted - at polling stops.
It's not just canines that offered a talking point on election day, when British broadcasters are banned from reporting on political news until polls close.
At the polling station where Miliband cast his vote, someone brought along a black lamb on a leash. Another voter linked an image of a horse, together with a woman in equestrian gear exiting the polling station.
Denmark's prime minister also popped into a British polling station - though she wasn't voting.
Helle Thorning-Schmidt was in South Wales to support her husband, Stephen Kinnock, a Labour Party candidate for the constituency of Aberavon.
A video posted on YouTube showed the couple emerging from a polling station after Kinnock cast his vote.
Asked how it felt to have a husband sitting in the parliament of another country, Thorning-Schmidt said she was happy for him because he worked hard campaigning.
"I don't know anyone who works as hard as Stephen," she said. "Today I am simply proud."
Asked how they would celebrate his win, she said: "Let's wait and see how things go today, but we will be very tense."